"Late night driving, people across seats sleeping without seat belts on," he said.

"There has been some injuries caused by not being restrained, so there's a message in that for everybody."

Bus line Greyhound says the company is shocked by the crash involving one of its coaches.

Greyhound says seat belts are fitted in all its buses and passengers are always asked to wear them.

Greyhound company spokesman Robert Thomas says recording equipment on the bus should help those investigating the crash.

"We have a full telematic system in there which can provide us details of braking, of steering, of speed and all of that sort of stuff, which makes it pretty easy to put together the exact details of the accident," he said.